The present invention relates generally to diagnostic imaging and, more particularly, to an apparatus and method of manufacturing an optical communication between a rotatable base and a stationary base of a CT gantry.
Typically, in computed tomography (CT) imaging systems, an x-ray source emits a fan-shaped beam toward a subject or object, such as a patient or a piece of luggage. Hereinafter, the terms “subject” and “object” shall include anything capable of being imaged. The beam, after being attenuated by the subject, impinges upon an array of radiation detectors. The intensity of the attenuated beam radiation received at the detector array is typically dependent upon the attenuation of the x-ray beam by the subject. Each detector element of the detector array produces a separate electrical signal indicative of the attenuated beam received by each detector element. The electrical signals are transmitted to a data processing system for analysis which ultimately produces an image.
A CT system typically includes a gantry to provide mechanical support and functionality to the CT system. The gantry typically includes a stationary mechanical base, a rotatable mechanical base, electronics (circuit boards, cable assemblies, and power supplies) mounted on the stationary mechanical base, electronics (circuit boards, cable assemblies, power supplies), and an x-ray source. Generally, the x-ray source and the detector array are mounted to the rotatable base and rotated about an imaging volume and about the subject. The x-ray source typically includes an x-ray tube, which emits an x-ray beam at a focal point.
The detector array typically includes a collimator for collimating x-ray beams received at the detector, a scintillator for converting x-rays to light energy adjacent the collimator, and a photodiode array for receiving the light energy from the adjacent scintillator and producing electrical signals therefrom. Typically, the scintillators are arranged in a scintillator array to convert x-rays to light energy. Each scintillator discharges light energy to a photodiode adjacent thereto. Each photodiode detects the light energy and generates a corresponding analog electrical signal which is then digitized and transmitted to the data processing system for image reconstruction.
Because the detector array is rotated with the rotatable base, digitized electrical signals generated therein may be transmitted from the rotatable base to the stationary base, where data processing and image reconstruction may take place. Such data is typically transmitted over a high-speed, capacitively coupled, unidirectional line. Additionally, software data and hardware commands are typically transmitted between the stationary base and the rotating base in order to control aspects of the system operations on the rotating base. Data is also often typically transmitted between the rotating side and the stationary side to provide, for instance, system status.
A brush-based system is typically used for carrying software generated TCP/IP data and hardware commands related to operation of the imaging system. Such systems are typically referred to as low-speed communication lines. Data transmitted on low-speed communication lines is typically binned in two ways:
1. Software generated TCP/IP data typically contains information needed by circuit boards on the rotating base of the gantry in order for the circuit boards to function correctly. Such information may include, for example, scan setup parameters, error log feedback, and status. The software data is typically transmitted bi-directionally. Thus, in a brush-based system, each direction of data transmission (i.e., to/from the rotating side) may use one sliding contact ring.
2. Hardware generated commands related to operation of the system is also typically transmitted via the brush-based system. Such information may include, for example, commands directing the system to turn on/off x-rays, and realtime encoder feedback from the stationary axial encoder to the DAS as trigger commands. The hardware generated commands are typically uni-directional and transmitted to the rotating base. The hardware commands are typically shared with the low-speed communication line that transmits the software generated TCP/IP data to the rotating base.
However, in recent years, gantry run speeds have been increasing. Because brush-based data transmission systems are wear items, communication between the stationary and rotating sides tends to degrade as the brushes wear, and the wear-rate increases with an increased gantry run speed. Brush-based systems also require periodic maintenance, such as cleaning and replacement of wear items, which adds overall cost to the system, the cost of which increases with gantry run speed. Furthermore, brush-to-ring tolerance requirements increase because faster gantry run speeds are more sensitive to brush-ring misalignment. Additionally, the ring in a brush-based system can serve as an antenna which can be a noise source that interferes with signals and data transmitting therethrough.
Finally, as gantry run speeds increase, so too does the required rate of hardware generated command transmission in the form of DAS trigger commands. Data transmission rates are regulated and limited, however, because of the emissions that radiate therefrom. Meeting regulated emission requirements is therefore increasingly difficult with increased gantry run speed.
Therefore, it would be desirable to design an apparatus and method of manufacturing a gantry communication system with greater communication bandwidth, increased noise immunity, brushless operation, and a modular design to provide bi-directional communications for software data and hardware commands between the rotating and stationary bases of a CT gantry.